Java Virtual Machine (Java Series) - page 49

Retrieves a byte from a byte array, expands it to an integer and places it on the operand stack. arrayref is a reference to an array of bytes. index is an int. The arrayref and index are removed from the stack, and the 8-bit signed byte at the given index in the array is retrieved, sign-extended to a 32-bit int, and pushed onto the stack.

baload is also used to retrieve values from boolean arrays. In this case, arrayref is a reference to an array of booleans (see the newarray instruction) . If the entry at the given index is true , then the int 1 is pushed onto the stack, otherwise the int 0 is pushed onto the stack. In Sun's implementation, boolean arrays are actually stored as byte arrays, using one byte per boolean value. Other implementations might use packed arrays - or even int arrays - this is invisible to programs running on the JVM, which always use baload and bastore to access and store values in boolean arrays.

Example

; This is like the Java code:
;     byte x = arr[0];
; where x is local variable 2 and arr is a byte array in local variable 1
aload_1       ; load local variable 1 onto the stack
iconst_0      ; push the integer 0 onto the stack
baload        ; retrieve the entry
istore_2      ; store the entry in local variable 2

NullPointerException - arrayref is null

ArrayIndexOutOfBoundsException - index is < 0 or >= arrayref.length

Bytecode